The present invention relates to a slice-ice machine of the type having a rotating freezing drum and means for supplying water to the outside of this drum, whereby the water is successively frozen on the drum surface and moved therewith past a scraper station, in which a knife bar cooperates with the freezing drum so as to scrape off the ice by a row of stationary scraper knives, which are held so as to project almost entirely into contact with the outside of the drum, generally tangentially thereto, though with a slight inclination relative the moving direction of the drum surface. Due to this inclination of the stationary scraper knives the ice is effectively broken, without any tendency of the knives to seek inwardly towards the drum surface by the reaction pressure of the ice, whereby the drum surface could be damaged.
It is both traditional and natural to make use of a freezing drum having a vertical axis of rotation, as ii is hereby easy to supply the water to the drum in a well defined manner from a supply area, from which the water runs down along the outside of the drum such that the water freezes before its successive arrival into the scraper station, which, viewed in the direction of rotation of the drum, may be placed immediately in front of the water supply area.
In the scraper station the ice will meet a vertical row of stationary scraper knives or edges, which, due to their inclination, will act to displace the ice in the falling direction thereof, and this is sufficient for the ice to be broken into slices adjacent the single scraper knives. Thus, by the horizontal passage of the ice past the vertical scraper knife bar the ice will be broken and loosened from the drum surface throughout the area downwardly along the knife bar. The slice breaking of the ice propagates down to a certain distance underneath the single scraper knives, such that these knives need not be mounted as close to each other as corresponding to an operative overlapping or filling out of the space along the knife bar, inasfar as the ice will be effectively scraped off even when there is a certain free spacing, viewed in the axial direction of the drum or the length direction of the knife bar, between the rear end of an overlying inclined scraper knife and the front end of an underlying inclined scraper knife. Hereby the ice along the entire drum surface as passing the knife bar may be scraped down by a reasonably small number of only slightly inclined scraper knives or edges.
In connection with the present invention it has been recognized that a disadvantage, which has so far been considered as a mere operational condition, exists in the scraping action of the knives giving rise to an opposite reaction force, which affects the knife bar upwardly, and in practice this effect is quite pronounced such that the knife bar and the holding means thereof must be rather heavily dimensioned, which is correspondingly true for the associated axial support of the drum as well as the drum itself, because the drum will experience, in total, a quite considerable downwardly directed influence from the scraper knives, through the ice. All according to the character or hardness of the applied water these forces may be even very high, particularly when the produced ice is extra ductile, and in a series production of the slice-ice machines it should be aforeseen, therefore, that each of the machines may be exposed to extreme operative conditions in this respect, i.e. all of the machines should be correspondingly heavily dimensioned.
Against this background it is the purpose of the invention to provide a slice-ice machine of the relevant type, in which the discussed forces may be reduced considerably, and according to the invention this is achieved by leaving or breaking with the traditional idea of the ice generally having to be scraped off the drum in the downward direction. According to the invention it is recognized that by a scraping off of the half of the ice in the upward direction it is possible to achieve a balancing between the forces seeking to push the knife bar upwardly and the freezing drum downwardly, respectively, as the forces will then be distributed such that no considerable resulting forces will act upon neither the knife bar nor the drum. Some of the ice will be scraped off upwardly, but this is entirely unimportant for the function or the efficiency of the machine.
Principally it would be possible to hereby make use of knives of alternating upward and downward inclination, but this could lead to efficiency problems between each pair of neighboring knives if the knives are mounted just above each other. Preferably, therefore, all the knives should be uniformly oriented along one half of the knife bar and oppositely uniformly oriented along the other half of the knife bar, whereby a special situation will occur at one place only, viz. adjacent the two middle knives, which will either converge against or diverge from each other, If they diverge from each other there may be left between them a zone of non-scraped-off ice, so it is preferred to arrange the knives such that the two middle knives converge towards each other with a suitable spacing between their rear ends, whereby all the ice in the middle zone may be scraped off by the scraping action along the upper and lower edge zones thereof.